chore(card10-board): Fix a sign-compare warning

Fix the following warning:

    lib/sdk/Libraries/Boards/card10/Source/board.c: In function 'Board_Init':
    lib/sdk/Libraries/Boards/card10/Source/board.c:102:19: warning:
             comparison of integer expressions of different signedness:
             'int' and 'unsigned int' [-Wsign-compare]
      102 |     for (i = 0; i < num_pins; i++) {
          |                   ^

Signed-off-by: Rahix <rahix@rahix.de>

lib/sdk/Libraries/Boards/card10/Source/board.c

@@ -98,7 +98,7 @@ int Board_Init(void)
         {PORT_0, PIN_31, GPIO_FUNC_OUT, GPIO_PAD_NONE},     // ECG switch
     };
     const unsigned int num_pins = (sizeof(pins) / sizeof(gpio_cfg_t));
-    int i;
+    unsigned int i;
     for (i = 0; i < num_pins; i++) {
         GPIO_OutClr(&pins[i]);
         GPIO_Config(&pins[i]);